T-Mobile is filing a request today with the FCC for a longer comment period on a proposed spectrum auction, claiming its network service would suffer interference if the spectrum is sold off.

The carrier also wants the federal agency to test whether using part of the 2.1GHz-band wireless spectrum -- known as Advanced Wireless Services 3 (AWS-3) and located adjacent to T-Mobile spectrum bought two years ago -- would interfere with the carrier's current network.

The FCC had set a 14-day comment time frame, which ends today, for feedback on the proposal. T-Mobile, which has already initiated its own testing, called the time frame "insufficient" for assessing the "complex issues" and wants a 90-day extension.

"The FCC is considering rules that would create a serious risk of severe interference on adjacent bands where licensees, including T-Mobile, have already spent billions of dollars to acquire spectrum and build wireless broadband networks," a T-Mobile spokesperson told InternetNews.com.

The spectrum debate comes as carriers are hungrier than ever for bigger network pipes to meet increasing wireless data demand by customers. The increasing appetite for spectrum resulted in the biggest sale ever earlier this year when the FCC raised nearly $20 billion in selling off a huge hunch of 700MHz band. According to industry group CTIA 84 percent of the U.S. population now uses wireless services.

T-Mobile, currently the fourth-largest U.S. carrier, paid a little more than $4 billion for the adjacent AWS spectrum.

"We're asking the FCC to give the industry additional time to do testing on the interference issues that exist," the spokesperson added. T-Mobile said preliminary lab tests demonstrate interference and that it needs more time to complete testing. The carrier has requested a 90-day extension until October.

A FCC spokesperson said it does not comment on filings and that interested parties can reply to submitted comments until Aug. 11.

In late June the FCC asked for feedback on AWS-3. A unique condition would have the winning bidder build a free Internet network accessible to 95 percent of the U.S. population within 10 years. It's the first time the FCC has proposed such a condition, according to an agency spokesperson.

The free Internet network aspect has already drawn opposition, with two Republican congressman calling for the provision to be removed, saying it would deter auction bidders and result in a low price.

In their letter to FCC Chairman Kevin Martin, the lawmakers, Joe Barton of Texas and Cliff Stearns of Florida, said the band could interfere with existing licenses in the neighboring spectrum.

Published reports claim AT&T Wireless, Verizon and the CTIA, a wireless industry advocacy group, are opposed to the free Internet condition. None returned calls for comment from InternetNews.com by press time.

While it wages its fight to get more spectrum testing time, T-Mobile also announced today that it has bought additional spectrum from Netwave Wireless for $98 million to advance its 3G network plans.